1. [Field of the Invention]
The present invention relates to a configuration of thin-film transistors (TFTs) formed on a flexible substrate (i.e., having mechanical flexibility) such as a resinous substrate which can be made of engineering plastics. The invention also relates to a method of fabricating such thin-film transistors. Furthermore, the invention relates to an active matrix liquid crystal display fabricated, using these thin-film transistors.
2. [Prior Art]
Thin-film transistors formed on glass substrates or on quartz substrates are known. Thin-film transistors formed on glass substrates are chiefly used in active matrix liquid crystal displays. Since active matrix liquid crystal displays can display images with high response and with high information content, it is expected that they can supplant simple matrix liquid crystal displays.
In an active matrix liquid crystal display, one or more thin-film transistors are disposed as a switching element at each pixel. Electric charge going in and out of the pixel electrode is controlled by this thin-film transistor. The substrates are made of glass or quartz, because it is necessary that visible light pass through the liquid crystal display.
Liquid crystal displays are display means which are expected to find quite extensive application. For example, they are expected to be used as display means for card-type computers, portable computers, and portable electronic devices for various telecommunication appliances. As more sophisticated information is treated, more sophisticated information is required to be displayed on the display means used for these portable electronic devices. For example, there is a demand for functions of displaying higher information content and moving pictures as well as numerals and symbols.
Where a liquid crystal display is required to have a function of displaying higher information content and moving pictures, it is necessary to utilize an active matrix liquid crystal display. However, where substrates made of glass or quartz are used, various problems take place: (1) limitations are imposed on thinning of the liquid crystal display itself; (2) the weight is increased; (3) if the thickness is reduced in an attempt to reduce the weight, the substrate breaks; and (4) the substrate lacks flexibility.
Especially, card-type electronic devices are required to be so flexible that they are not damaged if slight stress is exerted on them when they are treated. Therefore, liquid crystal displays incorporated in these electronic devices are similarly required to be flexible.
The invention disclosed herein provides an active matrix liquid crystal display having flexibility.